There are various applications in which it may be desirable to monitor the flow of multi-phase samples. For example, oil-in-water two-phase flows are often encountered in the petroleum industry. The measurement of phase flow rates is of particular importance for managing oil production and water disposal and/or water reinjection in the oil industry. The complexity of two and three-phase flow structures creates a challenge to flow measurements, and there is a constant need to improve flow monitoring systems in order to produce more accurate, more useful, and/or more reliable results, for example tomograms indicative of flow cross-sections with improved resolution and/or tomograms generated more rapidly/frequently with a particular data processing resource.
It is generally desirable to produce flow monitoring systems that are able to measure and provide a more accurate indication of various flow parameters of mixed-phase flows, and systems that are able to provide an indication of parameters that could not be deduced from previous systems and methods.
It is known for tomography apparatus to be used for monitoring flowing samples, and to produce tomograms indicative of a conductivity profile of a flowing sample across a conduit carrying sample, the apparatus employing arrays of electrodes distributed around the conduit in a wall. Such systems typically perform a plurality of measurements, using one pair of electrodes to drive a current through the flowing sample, and another pair of electrodes to measure a resultant voltage developed. From a large number of such measurements, using different pairs of electrodes, known calculation techniques are able to generate a tomogram indicative of the conductivity profile of a sample across the conduit bore. However, a problem with such systems is that samples material may be deposited on, or otherwise build up on the electrode contact surfaces. In general this build-up of material will generally increase the impedance of the electrode-sample connection/contact and can reduce the accuracy and/or resolution, or otherwise degrade the tomograms that could be generated from the measured data. This can be a particular problem in systems for use in the monitoring of two-phase sample flows, such as flows of oil mixed with water. Oil droplets, for example, may build up on the contact surfaces, degrading performance of the tomography apparatus as a whole.